A major problem in the study of human fertility has been the difficulty of exploiting information obtained from experimental animal systems. In the case of the estrogens, this difficulty has been due to the necessity of performing in vivo experiments. The tissue culture system we have developed for analysis of in vitro estrogen stimulation of the rat uterus holds promise that a similar system can be developed for human uterine tissue. As an index of hormonal responsiveness, we will monitor by specific immunoprecipitation techniques increases in uterine guanosine 3':5'- cyclic monophosphate levels, and the synthesis of a specific uterine estrogen-induced protein using physiological concentrations of estradiol in vitro. Efforts will be made to develop methods for long term culturing of human uterine cells to enable analysis of later estrogenic responses. Investigations will be conducted to correlate these and other early biochemical events with the uptake, cytoplasmic binding, and nuclear movement of various estrogens and estrogen derivatives, and compounds of contraceptive importance in this human "target" tissue. Efforts will be made to unambigously characterize nuclear versus cytoplasmic estrogen receptor. The functional and endocrine state (premenopausal, post- menopausal, normal, cancerous) of the uterus will be correlated with the tissue content of hormone and its subcellular distribution as determined by radioimmunoassay and with receptor pattern determined by specific receptor (exchange) assays. Development and characterization of a suitable in vitro system using human uterine tissue should enable significant progress to be made in understanding how the sex steroids function in human reproduction.